/*
 * Copyright (c) 2015 Grzegorz Kostka (kostka.grzegorz@gmail.com)
 * Copyright (c) 2015 Kaho Ng (ngkaho1234@gmail.com)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup lwext4
 * @{
 */
/**
 * @file  ext4_journal.c
 * @brief Journal handle functions
 */

#include <ext4_config.h>
#include <ext4_types.h>
#include <ext4_misc.h>
#include <ext4_errno.h>
#include <ext4_debug.h>

#include <ext4_fs.h>
#include <ext4_super.h>
#include <ext4_journal.h>
#include <ext4_blockdev.h>
#include <ext4_crc32.h>
#include <ext4_journal.h>

#include <libs/klibc.h>

/**@brief  Revoke entry during journal replay.*/
struct revoke_entry {
    /**@brief  Block number not to be replayed.*/
    ext4_fsblk_t block;

    /**@brief  For any transaction id smaller
     *         than trans_id, records of @block
     *         in those transactions should not
     *         be replayed.*/
    uint32_t trans_id;

    /**@brief  Revoke tree node.*/
    RB_ENTRY(revoke_entry)
    revoke_node;
};

/**@brief  Valid journal replay information.*/
struct recover_info {
    /**@brief  Starting transaction id.*/
    uint32_t start_trans_id;

    /**@brief  Ending transaction id.*/
    uint32_t last_trans_id;

    /**@brief  Used as internal argument.*/
    uint32_t this_trans_id;

    /**@brief  No of transactions went through.*/
    uint32_t trans_cnt;

    /**@brief  RB-Tree storing revoke entries.*/
    RB_HEAD(jbd_revoke, revoke_entry)
    revoke_root;
};

/**@brief  Journal replay internal arguments.*/
struct replay_arg {
    /**@brief  Journal replay information.*/
    struct recover_info *info;

    /**@brief  Current block we are on.*/
    uint32_t *this_block;

    /**@brief  Current trans_id we are on.*/
    uint32_t this_trans_id;
};

/* Make sure we wrap around the log correctly! */
#define wrap(sb, var)                                                          \
    do {                                                                       \
        if (var >= jbd_get32((sb), maxlen))                                    \
            var -= (jbd_get32((sb), maxlen) - jbd_get32((sb), first));         \
    } while (0)

static inline int32_t trans_id_diff(uint32_t x, uint32_t y) {
    int32_t diff = x - y;
    return diff;
}

static int jbd_revoke_entry_cmp(struct revoke_entry *a,
                                struct revoke_entry *b) {
    if (a->block > b->block)
        return 1;
    else if (a->block < b->block)
        return -1;
    return 0;
}

static int jbd_block_rec_cmp(struct jbd_block_rec *a, struct jbd_block_rec *b) {
    if (a->lba > b->lba)
        return 1;
    else if (a->lba < b->lba)
        return -1;
    return 0;
}

static int jbd_revoke_rec_cmp(struct jbd_revoke_rec *a,
                              struct jbd_revoke_rec *b) {
    if (a->lba > b->lba)
        return 1;
    else if (a->lba < b->lba)
        return -1;
    return 0;
}

RB_GENERATE_INTERNAL(jbd_revoke, revoke_entry, revoke_node,
                     jbd_revoke_entry_cmp, static inline)
RB_GENERATE_INTERNAL(jbd_block, jbd_block_rec, block_rec_node,
                     jbd_block_rec_cmp, static inline)
RB_GENERATE_INTERNAL(jbd_revoke_tree, jbd_revoke_rec, revoke_node,
                     jbd_revoke_rec_cmp, static inline)

#define jbd_alloc_revoke_entry() ext4_calloc(1, sizeof(struct revoke_entry))
#define jbd_free_revoke_entry(addr) ext4_free(addr)

static int jbd_has_csum(struct jbd_sb *jbd_sb) {
    if (JBD_HAS_INCOMPAT_FEATURE(jbd_sb, JBD_FEATURE_INCOMPAT_CSUM_V2))
        return 2;

    if (JBD_HAS_INCOMPAT_FEATURE(jbd_sb, JBD_FEATURE_INCOMPAT_CSUM_V3))
        return 3;

    return 0;
}

#if CONFIG_META_CSUM_ENABLE
static uint32_t jbd_sb_csum(struct jbd_sb *jbd_sb) {
    uint32_t checksum = 0;

    if (jbd_has_csum(jbd_sb)) {
        uint32_t orig_checksum = jbd_sb->checksum;
        jbd_set32(jbd_sb, checksum, 0);
        /* Calculate crc32c checksum against tho whole superblock */
        checksum = ext4_crc32c(EXT4_CRC32_INIT, jbd_sb, JBD_SUPERBLOCK_SIZE);
        jbd_sb->checksum = orig_checksum;
    }
    return checksum;
}
#else
#define jbd_sb_csum(...) 0
#endif

static void jbd_sb_csum_set(struct jbd_sb *jbd_sb) {
    if (!jbd_has_csum(jbd_sb))
        return;

    jbd_set32(jbd_sb, checksum, jbd_sb_csum(jbd_sb));
}

#if CONFIG_META_CSUM_ENABLE
static bool jbd_verify_sb_csum(struct jbd_sb *jbd_sb) {
    if (!jbd_has_csum(jbd_sb))
        return true;

    return jbd_sb_csum(jbd_sb) == jbd_get32(jbd_sb, checksum);
}
#else
#define jbd_verify_sb_csum(...) true
#endif

#if CONFIG_META_CSUM_ENABLE
static uint32_t jbd_meta_csum(struct jbd_fs *jbd_fs, struct jbd_bhdr *bhdr) {
    uint32_t checksum = 0;

    if (jbd_has_csum(&jbd_fs->sb)) {
        uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
        struct jbd_block_tail *tail =
            (struct jbd_block_tail *)((char *)bhdr + block_size -
                                      sizeof(struct jbd_block_tail));
        uint32_t orig_checksum = tail->checksum;
        tail->checksum = 0;

        /* First calculate crc32c checksum against fs uuid */
        checksum = ext4_crc32c(EXT4_CRC32_INIT, jbd_fs->sb.uuid,
                               sizeof(jbd_fs->sb.uuid));
        /* Calculate crc32c checksum against tho whole block */
        checksum = ext4_crc32c(checksum, bhdr, block_size);
        tail->checksum = orig_checksum;
    }
    return checksum;
}
#else
#define jbd_meta_csum(...) 0
#endif

static void jbd_meta_csum_set(struct jbd_fs *jbd_fs, struct jbd_bhdr *bhdr) {
    uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
    struct jbd_block_tail *tail =
        (struct jbd_block_tail *)((char *)bhdr + block_size -
                                  sizeof(struct jbd_block_tail));
    if (!jbd_has_csum(&jbd_fs->sb))
        return;

    tail->checksum = to_be32(jbd_meta_csum(jbd_fs, bhdr));
}

#if CONFIG_META_CSUM_ENABLE
static bool jbd_verify_meta_csum(struct jbd_fs *jbd_fs, struct jbd_bhdr *bhdr) {
    uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
    struct jbd_block_tail *tail =
        (struct jbd_block_tail *)((char *)bhdr + block_size -
                                  sizeof(struct jbd_block_tail));
    if (!jbd_has_csum(&jbd_fs->sb))
        return true;

    return jbd_meta_csum(jbd_fs, bhdr) == to_be32(tail->checksum);
}
#else
#define jbd_verify_meta_csum(...) true
#endif

#if CONFIG_META_CSUM_ENABLE
static uint32_t jbd_commit_csum(struct jbd_fs *jbd_fs,
                                struct jbd_commit_header *header) {
    uint32_t checksum = 0;

    if (jbd_has_csum(&jbd_fs->sb)) {
        uint8_t orig_checksum_type = header->chksum_type,
                orig_checksum_size = header->chksum_size;
        uint32_t orig_checksum = header->chksum[0];
        uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
        header->chksum_type = 0;
        header->chksum_size = 0;
        header->chksum[0] = 0;

        /* First calculate crc32c checksum against fs uuid */
        checksum = ext4_crc32c(EXT4_CRC32_INIT, jbd_fs->sb.uuid,
                               sizeof(jbd_fs->sb.uuid));
        /* Calculate crc32c checksum against tho whole block */
        checksum = ext4_crc32c(checksum, header, block_size);

        header->chksum_type = orig_checksum_type;
        header->chksum_size = orig_checksum_size;
        header->chksum[0] = orig_checksum;
    }
    return checksum;
}
#else
#define jbd_commit_csum(...) 0
#endif

static void jbd_commit_csum_set(struct jbd_fs *jbd_fs,
                                struct jbd_commit_header *header) {
    if (!jbd_has_csum(&jbd_fs->sb))
        return;

    header->chksum_type = 0;
    header->chksum_size = 0;
    header->chksum[0] = jbd_commit_csum(jbd_fs, header);
}

#if CONFIG_META_CSUM_ENABLE
static bool jbd_verify_commit_csum(struct jbd_fs *jbd_fs,
                                   struct jbd_commit_header *header) {
    if (!jbd_has_csum(&jbd_fs->sb))
        return true;

    return header->chksum[0] == to_be32(jbd_commit_csum(jbd_fs, header));
}
#else
#define jbd_verify_commit_csum(...) true
#endif

#if CONFIG_META_CSUM_ENABLE
/*
 * NOTE: We only make use of @csum parameter when
 *       JBD_FEATURE_COMPAT_CHECKSUM is enabled.
 */
static uint32_t jbd_block_csum(struct jbd_fs *jbd_fs, const void *buf,
                               uint32_t csum, uint32_t sequence) {
    uint32_t checksum = 0;

    if (jbd_has_csum(&jbd_fs->sb)) {
        uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
        /* First calculate crc32c checksum against fs uuid */
        checksum = ext4_crc32c(EXT4_CRC32_INIT, jbd_fs->sb.uuid,
                               sizeof(jbd_fs->sb.uuid));
        /* Then calculate crc32c checksum against sequence no. */
        checksum = ext4_crc32c(checksum, &sequence, sizeof(uint32_t));
        /* Calculate crc32c checksum against tho whole block */
        checksum = ext4_crc32c(checksum, buf, block_size);
    } else if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb,
                                        JBD_FEATURE_COMPAT_CHECKSUM)) {
        uint32_t block_size = jbd_get32(&jbd_fs->sb, blocksize);
        /* Calculate crc32c checksum against tho whole block */
        checksum = ext4_crc32(csum, buf, block_size);
    }
    return checksum;
}
#else
#define jbd_block_csum(...) 0
#endif

static void jbd_block_tag_csum_set(struct jbd_fs *jbd_fs, void *__tag,
                                   uint32_t checksum) {
    int ver = jbd_has_csum(&jbd_fs->sb);
    if (!ver)
        return;

    if (ver == 2) {
        struct jbd_block_tag *tag = __tag;
        tag->checksum = (uint16_t)to_be32(checksum);
    } else {
        struct jbd_block_tag3 *tag = __tag;
        tag->checksum = to_be32(checksum);
    }
}

/**@brief  Write jbd superblock to disk.
 * @param  jbd_fs jbd filesystem
 * @param  s jbd superblock
 * @return standard error code*/
static int jbd_sb_write(struct jbd_fs *jbd_fs, struct jbd_sb *s) {
    int rc;
    struct ext4_fs *fs = jbd_fs->inode_ref.fs;
    uint64_t offset;
    ext4_fsblk_t fblock;
    rc = jbd_inode_bmap(jbd_fs, 0, &fblock);
    if (rc != EOK)
        return rc;

    jbd_sb_csum_set(s);
    offset = fblock * ext4_sb_get_block_size(&fs->sb);
    return ext4_block_writebytes(fs->bdev, offset, s, EXT4_SUPERBLOCK_SIZE);
}

/**@brief  Read jbd superblock from disk.
 * @param  jbd_fs jbd filesystem
 * @param  s jbd superblock
 * @return standard error code*/
static int jbd_sb_read(struct jbd_fs *jbd_fs, struct jbd_sb *s) {
    int rc;
    struct ext4_fs *fs = jbd_fs->inode_ref.fs;
    uint64_t offset;
    ext4_fsblk_t fblock;
    rc = jbd_inode_bmap(jbd_fs, 0, &fblock);
    if (rc != EOK)
        return rc;

    offset = fblock * ext4_sb_get_block_size(&fs->sb);
    return ext4_block_readbytes(fs->bdev, offset, s, EXT4_SUPERBLOCK_SIZE);
}

/**@brief  Verify jbd superblock.
 * @param  sb jbd superblock
 * @return true if jbd superblock is valid */
static bool jbd_verify_sb(struct jbd_sb *sb) {
    struct jbd_bhdr *header = &sb->header;
    if (jbd_get32(header, magic) != JBD_MAGIC_NUMBER)
        return false;

    if (jbd_get32(header, blocktype) != JBD_SUPERBLOCK &&
        jbd_get32(header, blocktype) != JBD_SUPERBLOCK_V2)
        return false;

    return jbd_verify_sb_csum(sb);
}

/**@brief  Write back dirty jbd superblock to disk.
 * @param  jbd_fs jbd filesystem
 * @return standard error code*/
static int jbd_write_sb(struct jbd_fs *jbd_fs) {
    int rc = EOK;
    if (jbd_fs->dirty) {
        rc = jbd_sb_write(jbd_fs, &jbd_fs->sb);
        if (rc != EOK)
            return rc;

        jbd_fs->dirty = false;
    }
    return rc;
}

/**@brief  Get reference to jbd filesystem.
 * @param  fs Filesystem to load journal of
 * @param  jbd_fs jbd filesystem
 * @return standard error code*/
int jbd_get_fs(struct ext4_fs *fs, struct jbd_fs *jbd_fs) {
    int rc;
    uint32_t journal_ino;

    memset(jbd_fs, 0, sizeof(struct jbd_fs));
    /* See if there is journal inode on this filesystem.*/
    /* FIXME: detection on existance ofbkejournal bdev is
     *        missing.*/
    journal_ino = ext4_get32(&fs->sb, journal_inode_number);

    rc = ext4_fs_get_inode_ref(fs, journal_ino, &jbd_fs->inode_ref);
    if (rc != EOK)
        return rc;

    rc = jbd_sb_read(jbd_fs, &jbd_fs->sb);
    if (rc != EOK)
        goto Error;

    if (!jbd_verify_sb(&jbd_fs->sb)) {
        rc = EIO;
        goto Error;
    }

    if (rc == EOK)
        jbd_fs->bdev = fs->bdev;

    return rc;
Error:
    ext4_fs_put_inode_ref(&jbd_fs->inode_ref);
    memset(jbd_fs, 0, sizeof(struct jbd_fs));

    return rc;
}

/**@brief  Put reference of jbd filesystem.
 * @param  jbd_fs jbd filesystem
 * @return standard error code*/
int jbd_put_fs(struct jbd_fs *jbd_fs) {
    int rc = EOK;
    rc = jbd_write_sb(jbd_fs);

    ext4_fs_put_inode_ref(&jbd_fs->inode_ref);
    return rc;
}

/**@brief  Data block lookup helper.
 * @param  jbd_fs jbd filesystem
 * @param  iblock block index
 * @param  fblock logical block address
 * @return standard error code*/
int jbd_inode_bmap(struct jbd_fs *jbd_fs, ext4_lblk_t iblock,
                   ext4_fsblk_t *fblock) {
    int rc =
        ext4_fs_get_inode_dblk_idx(&jbd_fs->inode_ref, iblock, fblock, false);
    return rc;
}

/**@brief   jbd block get function (through cache).
 * @param   jbd_fs jbd filesystem
 * @param   block block descriptor
 * @param   fblock jbd logical block address
 * @return  standard error code*/
static int jbd_block_get(struct jbd_fs *jbd_fs, struct ext4_block *block,
                         ext4_fsblk_t fblock) {
    /* TODO: journal device. */
    int rc;
    struct ext4_blockdev *bdev = jbd_fs->bdev;
    ext4_lblk_t iblock = (ext4_lblk_t)fblock;

    /* Lookup the logical block address of
     * fblock.*/
    rc = jbd_inode_bmap(jbd_fs, iblock, &fblock);
    if (rc != EOK)
        return rc;

    rc = ext4_block_get(bdev, block, fblock);

    /* If succeeded, mark buffer as BC_FLUSH to indicate
     * that data should be written to disk immediately.*/
    if (rc == EOK) {
        ext4_bcache_set_flag(block->buf, BC_FLUSH);
        /* As we don't want to occupy too much space
         * in block cache, we set this buffer BC_TMP.*/
        ext4_bcache_set_flag(block->buf, BC_TMP);
    }

    return rc;
}

/**@brief   jbd block get function (through cache, don't read).
 * @param   jbd_fs jbd filesystem
 * @param   block block descriptor
 * @param   fblock jbd logical block address
 * @return  standard error code*/
static int jbd_block_get_noread(struct jbd_fs *jbd_fs, struct ext4_block *block,
                                ext4_fsblk_t fblock) {
    /* TODO: journal device. */
    int rc;
    struct ext4_blockdev *bdev = jbd_fs->bdev;
    ext4_lblk_t iblock = (ext4_lblk_t)fblock;
    rc = jbd_inode_bmap(jbd_fs, iblock, &fblock);
    if (rc != EOK)
        return rc;

    rc = ext4_block_get_noread(bdev, block, fblock);
    if (rc == EOK)
        ext4_bcache_set_flag(block->buf, BC_FLUSH);

    return rc;
}

/**@brief   jbd block set procedure (through cache).
 * @param   jbd_fs jbd filesystem
 * @param   block block descriptor
 * @return  standard error code*/
static int jbd_block_set(struct jbd_fs *jbd_fs, struct ext4_block *block) {
    struct ext4_blockdev *bdev = jbd_fs->bdev;
    return ext4_block_set(bdev, block);
}

/**@brief  helper functions to calculate
 *         block tag size, not including UUID part.
 * @param  jbd_fs jbd filesystem
 * @return tag size in bytes*/
static int jbd_tag_bytes(struct jbd_fs *jbd_fs) {
    int size;

    /* It is very easy to deal with the case which
     * JBD_FEATURE_INCOMPAT_CSUM_V3 is enabled.*/
    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V3))
        return sizeof(struct jbd_block_tag3);

    size = sizeof(struct jbd_block_tag);

    /* If JBD_FEATURE_INCOMPAT_CSUM_V2 is enabled,
     * add 2 bytes to size.*/
    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V2))
        size += sizeof(uint16_t);

    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
        return size;

    /* If block number is 4 bytes in size,
     * minus 4 bytes from size */
    return size - sizeof(uint32_t);
}

/**@brief  Tag information. */
struct tag_info {
    /**@brief  Tag size in bytes, including UUID part.*/
    int tag_bytes;

    /**@brief  block number stored in this tag.*/
    ext4_fsblk_t block;

    /**@brief  Is the first 4 bytes of block equals to
     *	   JBD_MAGIC_NUMBER? */
    bool is_escape;

    /**@brief  whether UUID part exists or not.*/
    bool uuid_exist;

    /**@brief  UUID content if UUID part exists.*/
    uint8_t uuid[UUID_SIZE];

    /**@brief  Is this the last tag? */
    bool last_tag;

    /**@brief  crc32c checksum. */
    uint32_t checksum;
};

/**@brief  Extract information from a block tag.
 * @param  __tag pointer to the block tag
 * @param  tag_bytes block tag size of this jbd filesystem
 * @param  remain_buf_size size in buffer containing the block tag
 * @param  tag_info information of this tag.
 * @return  EOK when succeed, otherwise return EINVAL.*/
static int jbd_extract_block_tag(struct jbd_fs *jbd_fs, void *__tag,
                                 int tag_bytes, int32_t remain_buf_size,
                                 struct tag_info *tag_info) {
    char *uuid_start;
    tag_info->tag_bytes = tag_bytes;
    tag_info->uuid_exist = false;
    tag_info->last_tag = false;
    tag_info->is_escape = false;

    /* See whether it is possible to hold a valid block tag.*/
    if (remain_buf_size - tag_bytes < 0)
        return EINVAL;

    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V3)) {
        struct jbd_block_tag3 *tag = __tag;
        tag_info->block = jbd_get32(tag, blocknr);
        if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
            tag_info->block |= (uint64_t)jbd_get32(tag, blocknr_high) << 32;

        if (jbd_get32(tag, flags) & JBD_FLAG_ESCAPE)
            tag_info->is_escape = true;

        if (!(jbd_get32(tag, flags) & JBD_FLAG_SAME_UUID)) {
            /* See whether it is possible to hold UUID part.*/
            if (remain_buf_size - tag_bytes < UUID_SIZE)
                return EINVAL;

            uuid_start = (char *)tag + tag_bytes;
            tag_info->uuid_exist = true;
            tag_info->tag_bytes += UUID_SIZE;
            memcpy(tag_info->uuid, uuid_start, UUID_SIZE);
        }

        if (jbd_get32(tag, flags) & JBD_FLAG_LAST_TAG)
            tag_info->last_tag = true;
    } else {
        struct jbd_block_tag *tag = __tag;
        tag_info->block = jbd_get32(tag, blocknr);
        if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
            tag_info->block |= (uint64_t)jbd_get32(tag, blocknr_high) << 32;

        if (jbd_get16(tag, flags) & JBD_FLAG_ESCAPE)
            tag_info->is_escape = true;

        if (!(jbd_get16(tag, flags) & JBD_FLAG_SAME_UUID)) {
            /* See whether it is possible to hold UUID part.*/
            if (remain_buf_size - tag_bytes < UUID_SIZE)
                return EINVAL;

            uuid_start = (char *)tag + tag_bytes;
            tag_info->uuid_exist = true;
            tag_info->tag_bytes += UUID_SIZE;
            memcpy(tag_info->uuid, uuid_start, UUID_SIZE);
        }

        if (jbd_get16(tag, flags) & JBD_FLAG_LAST_TAG)
            tag_info->last_tag = true;
    }
    return EOK;
}

/**@brief  Write information to a block tag.
 * @param  __tag pointer to the block tag
 * @param  remain_buf_size size in buffer containing the block tag
 * @param  tag_info information of this tag.
 * @return  EOK when succeed, otherwise return EINVAL.*/
static int jbd_write_block_tag(struct jbd_fs *jbd_fs, void *__tag,
                               int32_t remain_buf_size,
                               struct tag_info *tag_info) {
    char *uuid_start;
    int tag_bytes = jbd_tag_bytes(jbd_fs);

    tag_info->tag_bytes = tag_bytes;

    /* See whether it is possible to hold a valid block tag.*/
    if (remain_buf_size - tag_bytes < 0)
        return EINVAL;

    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V3)) {
        struct jbd_block_tag3 *tag = __tag;
        memset(tag, 0, sizeof(struct jbd_block_tag3));
        jbd_set32(tag, blocknr, (uint32_t)tag_info->block);
        if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
            jbd_set32(tag, blocknr_high, tag_info->block >> 32);

        if (tag_info->uuid_exist) {
            /* See whether it is possible to hold UUID part.*/
            if (remain_buf_size - tag_bytes < UUID_SIZE)
                return EINVAL;

            uuid_start = (char *)tag + tag_bytes;
            tag_info->tag_bytes += UUID_SIZE;
            memcpy(uuid_start, tag_info->uuid, UUID_SIZE);
        } else
            jbd_set32(tag, flags, jbd_get32(tag, flags) | JBD_FLAG_SAME_UUID);

        jbd_block_tag_csum_set(jbd_fs, __tag, tag_info->checksum);

        if (tag_info->last_tag)
            jbd_set32(tag, flags, jbd_get32(tag, flags) | JBD_FLAG_LAST_TAG);

        if (tag_info->is_escape)
            jbd_set32(tag, flags, jbd_get32(tag, flags) | JBD_FLAG_ESCAPE);
    } else {
        struct jbd_block_tag *tag = __tag;
        memset(tag, 0, sizeof(struct jbd_block_tag));
        jbd_set32(tag, blocknr, (uint32_t)tag_info->block);
        if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
            jbd_set32(tag, blocknr_high, tag_info->block >> 32);

        if (tag_info->uuid_exist) {
            /* See whether it is possible to hold UUID part.*/
            if (remain_buf_size - tag_bytes < UUID_SIZE)
                return EINVAL;

            uuid_start = (char *)tag + tag_bytes;
            tag_info->tag_bytes += UUID_SIZE;
            memcpy(uuid_start, tag_info->uuid, UUID_SIZE);
        } else
            jbd_set16(tag, flags, jbd_get16(tag, flags) | JBD_FLAG_SAME_UUID);

        jbd_block_tag_csum_set(jbd_fs, __tag, tag_info->checksum);

        if (tag_info->last_tag)
            jbd_set16(tag, flags, jbd_get16(tag, flags) | JBD_FLAG_LAST_TAG);

        if (tag_info->is_escape)
            jbd_set16(tag, flags, jbd_get16(tag, flags) | JBD_FLAG_ESCAPE);
    }
    return EOK;
}

/**@brief  Iterate all block tags in a block.
 * @param  jbd_fs jbd filesystem
 * @param  __tag_start pointer to the block
 * @param  tag_tbl_size size of the block
 * @param  func callback routine to indicate that
 *         a block tag is found
 * @param  arg additional argument to be passed to func */
static void jbd_iterate_block_table(
    struct jbd_fs *jbd_fs, void *__tag_start, int32_t tag_tbl_size,
    void (*func)(struct jbd_fs *jbd_fs, struct tag_info *tag_info, void *arg),
    void *arg) {
    char *tag_start, *tag_ptr;
    int tag_bytes = jbd_tag_bytes(jbd_fs);
    tag_start = __tag_start;
    tag_ptr = tag_start;

    /* Cut off the size of block tail storing checksum. */
    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V2) ||
        JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_CSUM_V3))
        tag_tbl_size -= sizeof(struct jbd_block_tail);

    while (tag_tbl_size) {
        struct tag_info tag_info;
        int rc = jbd_extract_block_tag(jbd_fs, tag_ptr, tag_bytes, tag_tbl_size,
                                       &tag_info);
        if (rc != EOK)
            break;

        if (func)
            func(jbd_fs, &tag_info, arg);

        /* Stop the iteration when we reach the last tag. */
        if (tag_info.last_tag)
            break;

        tag_ptr += tag_info.tag_bytes;
        tag_tbl_size -= tag_info.tag_bytes;
    }
}

static void jbd_display_block_tags(struct jbd_fs *jbd_fs,
                                   struct tag_info *tag_info, void *arg) {
    uint32_t *iblock = arg;
    ext4_dbg(DEBUG_JBD, "Block in block_tag: %" PRIu64 "\n", tag_info->block);
    (*iblock)++;
    wrap(&jbd_fs->sb, *iblock);
    (void)jbd_fs;
    return;
}

static struct revoke_entry *jbd_revoke_entry_lookup(struct recover_info *info,
                                                    ext4_fsblk_t block) {
    struct revoke_entry tmp = {.block = block};

    return RB_FIND(jbd_revoke, &info->revoke_root, &tmp);
}

/**@brief  Replay a block in a transaction.
 * @param  jbd_fs jbd filesystem
 * @param  tag_info tag_info of the logged block.*/
static void jbd_replay_block_tags(struct jbd_fs *jbd_fs,
                                  struct tag_info *tag_info, void *__arg) {
    int r;
    struct replay_arg *arg = __arg;
    struct recover_info *info = arg->info;
    uint32_t *this_block = arg->this_block;
    struct revoke_entry *revoke_entry;
    struct ext4_block journal_block, ext4_block;
    struct ext4_fs *fs = jbd_fs->inode_ref.fs;

    (*this_block)++;
    wrap(&jbd_fs->sb, *this_block);

    /* We replay this block only if the current transaction id
     * is equal or greater than that in revoke entry.*/
    revoke_entry = jbd_revoke_entry_lookup(info, tag_info->block);
    if (revoke_entry &&
        trans_id_diff(arg->this_trans_id, revoke_entry->trans_id) <= 0)
        return;

    ext4_dbg(DEBUG_JBD, "Replaying block in block_tag: %" PRIu64 "\n",
             tag_info->block);

    r = jbd_block_get(jbd_fs, &journal_block, *this_block);
    if (r != EOK)
        return;

    /* We need special treatment for ext4 superblock. */
    if (tag_info->block) {
        r = ext4_block_get_noread(fs->bdev, &ext4_block, tag_info->block);
        if (r != EOK) {
            jbd_block_set(jbd_fs, &journal_block);
            return;
        }

        memcpy(ext4_block.data, journal_block.data,
               jbd_get32(&jbd_fs->sb, blocksize));

        if (tag_info->is_escape)
            ((struct jbd_bhdr *)ext4_block.data)->magic =
                to_be32(JBD_MAGIC_NUMBER);

        ext4_bcache_set_dirty(ext4_block.buf);
        ext4_block_set(fs->bdev, &ext4_block);
    } else {
        uint16_t mount_count, state;
        mount_count = ext4_get16(&fs->sb, mount_count);
        state = ext4_get16(&fs->sb, state);

        memcpy(&fs->sb, journal_block.data + EXT4_SUPERBLOCK_OFFSET,
               EXT4_SUPERBLOCK_SIZE);

        /* Mark system as mounted */
        ext4_set16(&fs->sb, state, state);
        r = ext4_sb_write(fs->bdev, &fs->sb);
        if (r != EOK)
            return;

        /*Update mount count*/
        ext4_set16(&fs->sb, mount_count, mount_count);
    }

    jbd_block_set(jbd_fs, &journal_block);

    return;
}

/**@brief  Add block address to revoke tree, along with
 *         its transaction id.
 * @param  info  journal replay info
 * @param  block  block address to be replayed.*/
static void jbd_add_revoke_block_tags(struct recover_info *info,
                                      ext4_fsblk_t block) {
    struct revoke_entry *revoke_entry;

    ext4_dbg(DEBUG_JBD, "Add block %" PRIu64 " to revoke tree\n", block);
    /* If the revoke entry with respect to the block address
     * exists already, update its transaction id.*/
    revoke_entry = jbd_revoke_entry_lookup(info, block);
    if (revoke_entry) {
        revoke_entry->trans_id = info->this_trans_id;
        return;
    }

    revoke_entry = jbd_alloc_revoke_entry();
    ext4_assert(revoke_entry);
    revoke_entry->block = block;
    revoke_entry->trans_id = info->this_trans_id;
    RB_INSERT(jbd_revoke, &info->revoke_root, revoke_entry);

    return;
}

static void jbd_destroy_revoke_tree(struct recover_info *info) {
    while (!RB_EMPTY(&info->revoke_root)) {
        struct revoke_entry *revoke_entry =
            RB_MIN(jbd_revoke, &info->revoke_root);
        ext4_assert(revoke_entry);
        RB_REMOVE(jbd_revoke, &info->revoke_root, revoke_entry);
        jbd_free_revoke_entry(revoke_entry);
    }
}

#define ACTION_SCAN 0
#define ACTION_REVOKE 1
#define ACTION_RECOVER 2

/**@brief  Add entries in a revoke block to revoke tree.
 * @param  jbd_fs jbd filesystem
 * @param  header revoke block header
 * @param  info  journal replay info*/
static void jbd_build_revoke_tree(struct jbd_fs *jbd_fs,
                                  struct jbd_bhdr *header,
                                  struct recover_info *info) {
    char *blocks_entry;
    struct jbd_revoke_header *revoke_hdr = (struct jbd_revoke_header *)header;
    uint32_t i, nr_entries, record_len = 4;

    /* If we are working on a 64bit jbd filesystem, */
    if (JBD_HAS_INCOMPAT_FEATURE(&jbd_fs->sb, JBD_FEATURE_INCOMPAT_64BIT))
        record_len = 8;

    nr_entries =
        (jbd_get32(revoke_hdr, count) - sizeof(struct jbd_revoke_header)) /
        record_len;

    blocks_entry = (char *)(revoke_hdr + 1);

    for (i = 0; i < nr_entries; i++) {
        if (record_len == 8) {
            uint64_t *blocks = (uint64_t *)blocks_entry;
            jbd_add_revoke_block_tags(info, to_be64(*blocks));
        } else {
            uint32_t *blocks = (uint32_t *)blocks_entry;
            jbd_add_revoke_block_tags(info, to_be32(*blocks));
        }
        blocks_entry += record_len;
    }
}

static void jbd_debug_descriptor_block(struct jbd_fs *jbd_fs,
                                       struct jbd_bhdr *header,
                                       uint32_t *iblock) {
    jbd_iterate_block_table(jbd_fs, header + 1,
                            jbd_get32(&jbd_fs->sb, blocksize) -
                                sizeof(struct jbd_bhdr),
                            jbd_display_block_tags, iblock);
}

static void jbd_replay_descriptor_block(struct jbd_fs *jbd_fs,
                                        struct jbd_bhdr *header,
                                        struct replay_arg *arg) {
    jbd_iterate_block_table(jbd_fs, header + 1,
                            jbd_get32(&jbd_fs->sb, blocksize) -
                                sizeof(struct jbd_bhdr),
                            jbd_replay_block_tags, arg);
}

/**@brief  The core routine of journal replay.
 * @param  jbd_fs jbd filesystem
 * @param  info  journal replay info
 * @param  action action needed to be taken
 * @return standard error code*/
static int jbd_iterate_log(struct jbd_fs *jbd_fs, struct recover_info *info,
                           int action) {
    int r = EOK;
    bool log_end = false;
    struct jbd_sb *sb = &jbd_fs->sb;
    uint32_t start_trans_id, this_trans_id;
    uint32_t start_block, this_block;

    /* We start iterating valid blocks in the whole journal.*/
    start_trans_id = this_trans_id = jbd_get32(sb, sequence);
    start_block = this_block = jbd_get32(sb, start);
    if (action == ACTION_SCAN)
        info->trans_cnt = 0;
    else if (!info->trans_cnt)
        log_end = true;

    ext4_dbg(DEBUG_JBD, "Start of journal at trans id: %" PRIu32 "\n",
             start_trans_id);

    while (!log_end) {
        struct ext4_block block;
        struct jbd_bhdr *header;
        /* If we are not scanning for the last
         * valid transaction in the journal,
         * we will stop when we reach the end of
         * the journal.*/
        if (action != ACTION_SCAN)
            if (trans_id_diff(this_trans_id, info->last_trans_id) > 0) {
                log_end = true;
                continue;
            }

        r = jbd_block_get(jbd_fs, &block, this_block);
        if (r != EOK)
            break;

        header = (struct jbd_bhdr *)block.data;
        /* This block does not have a valid magic number,
         * so we have reached the end of the journal.*/
        if (jbd_get32(header, magic) != JBD_MAGIC_NUMBER) {
            jbd_block_set(jbd_fs, &block);
            log_end = true;
            continue;
        }

        /* If the transaction id we found is not expected,
         * we may have reached the end of the journal.
         *
         * If we are not scanning the journal, something
         * bad might have taken place. :-( */
        if (jbd_get32(header, sequence) != this_trans_id) {
            if (action != ACTION_SCAN)
                r = EIO;

            jbd_block_set(jbd_fs, &block);
            log_end = true;
            continue;
        }

        switch (jbd_get32(header, blocktype)) {
        case JBD_DESCRIPTOR_BLOCK:
            if (!jbd_verify_meta_csum(jbd_fs, header)) {
                ext4_dbg(DEBUG_JBD,
                         DBG_WARN "Descriptor block checksum failed."
                                  "Journal block: %" PRIu32 "\n",
                         this_block);
                log_end = true;
                break;
            }
            ext4_dbg(DEBUG_JBD,
                     "Descriptor block: %" PRIu32 ", "
                     "trans_id: %" PRIu32 "\n",
                     this_block, this_trans_id);
            if (action == ACTION_RECOVER) {
                struct replay_arg replay_arg;
                replay_arg.info = info;
                replay_arg.this_block = &this_block;
                replay_arg.this_trans_id = this_trans_id;

                jbd_replay_descriptor_block(jbd_fs, header, &replay_arg);
            } else
                jbd_debug_descriptor_block(jbd_fs, header, &this_block);

            break;
        case JBD_COMMIT_BLOCK:
            if (!jbd_verify_commit_csum(jbd_fs,
                                        (struct jbd_commit_header *)header)) {
                ext4_dbg(DEBUG_JBD,
                         DBG_WARN "Commit block checksum failed."
                                  "Journal block: %" PRIu32 "\n",
                         this_block);
                log_end = true;
                break;
            }
            ext4_dbg(DEBUG_JBD,
                     "Commit block: %" PRIu32 ", "
                     "trans_id: %" PRIu32 "\n",
                     this_block, this_trans_id);
            /*
             * This is the end of a transaction,
             * we may now proceed to the next transaction.
             */
            this_trans_id++;
            if (action == ACTION_SCAN)
                info->trans_cnt++;
            break;
        case JBD_REVOKE_BLOCK:
            if (!jbd_verify_meta_csum(jbd_fs, header)) {
                ext4_dbg(DEBUG_JBD,
                         DBG_WARN "Revoke block checksum failed."
                                  "Journal block: %" PRIu32 "\n",
                         this_block);
                log_end = true;
                break;
            }
            ext4_dbg(DEBUG_JBD,
                     "Revoke block: %" PRIu32 ", "
                     "trans_id: %" PRIu32 "\n",
                     this_block, this_trans_id);
            if (action == ACTION_REVOKE) {
                info->this_trans_id = this_trans_id;
                jbd_build_revoke_tree(jbd_fs, header, info);
            }
            break;
        default:
            log_end = true;
            break;
        }
        jbd_block_set(jbd_fs, &block);
        this_block++;
        wrap(sb, this_block);
        if (this_block == start_block)
            log_end = true;
    }
    ext4_dbg(DEBUG_JBD, "End of journal.\n");
    if (r == EOK && action == ACTION_SCAN) {
        /* We have finished scanning the journal. */
        info->start_trans_id = start_trans_id;
        if (trans_id_diff(this_trans_id, start_trans_id) > 0)
            info->last_trans_id = this_trans_id - 1;
        else
            info->last_trans_id = this_trans_id;
    }

    return r;
}

/**@brief  Replay journal.
 * @param  jbd_fs jbd filesystem
 * @return standard error code*/
int jbd_recover(struct jbd_fs *jbd_fs) {
    int r;
    struct recover_info info;
    struct jbd_sb *sb = &jbd_fs->sb;
    if (!sb->start)
        return EOK;

    RB_INIT(&info.revoke_root);

    r = jbd_iterate_log(jbd_fs, &info, ACTION_SCAN);
    if (r != EOK)
        return r;

    r = jbd_iterate_log(jbd_fs, &info, ACTION_REVOKE);
    if (r != EOK)
        return r;

    r = jbd_iterate_log(jbd_fs, &info, ACTION_RECOVER);
    if (r == EOK) {
        /* If we successfully replay the journal,
         * clear EXT4_FINCOM_RECOVER flag on the
         * ext4 superblock, and set the start of
         * journal to 0.*/
        uint32_t features_incompatible =
            ext4_get32(&jbd_fs->inode_ref.fs->sb, features_incompatible);
        jbd_set32(&jbd_fs->sb, start, 0);
        jbd_set32(&jbd_fs->sb, sequence, info.last_trans_id);
        features_incompatible &= ~EXT4_FINCOM_RECOVER;
        ext4_set32(&jbd_fs->inode_ref.fs->sb, features_incompatible,
                   features_incompatible);
        jbd_fs->dirty = true;
        r = ext4_sb_write(jbd_fs->bdev, &jbd_fs->inode_ref.fs->sb);
    }
    jbd_destroy_revoke_tree(&info);
    return r;
}

static void jbd_journal_write_sb(struct jbd_journal *journal) {
    struct jbd_fs *jbd_fs = journal->jbd_fs;
    jbd_set32(&jbd_fs->sb, start, journal->start);
    jbd_set32(&jbd_fs->sb, sequence, journal->trans_id);
    jbd_fs->dirty = true;
}

/**@brief  Start accessing the journal.
 * @param  jbd_fs jbd filesystem
 * @param  journal current journal session
 * @return standard error code*/
int jbd_journal_start(struct jbd_fs *jbd_fs, struct jbd_journal *journal) {
    int r;
    uint32_t features_incompatible =
        ext4_get32(&jbd_fs->inode_ref.fs->sb, features_incompatible);
    features_incompatible |= EXT4_FINCOM_RECOVER;
    ext4_set32(&jbd_fs->inode_ref.fs->sb, features_incompatible,
               features_incompatible);
    r = ext4_sb_write(jbd_fs->bdev, &jbd_fs->inode_ref.fs->sb);
    if (r != EOK)
        return r;

    journal->first = jbd_get32(&jbd_fs->sb, first);
    journal->start = journal->first;
    journal->last = journal->first;
    /*
     * To invalidate any stale records we need to start from
     * the checkpoint transaction ID of the previous journalling session
     * plus 1.
     */
    journal->trans_id = jbd_get32(&jbd_fs->sb, sequence) + 1;
    journal->alloc_trans_id = journal->trans_id;

    journal->block_size = jbd_get32(&jbd_fs->sb, blocksize);

    TAILQ_INIT(&journal->cp_queue);
    RB_INIT(&journal->block_rec_root);
    journal->jbd_fs = jbd_fs;
    jbd_journal_write_sb(journal);
    r = jbd_write_sb(jbd_fs);
    if (r != EOK)
        return r;

    jbd_fs->bdev->journal = journal;
    return EOK;
}

static void jbd_trans_end_write(struct ext4_bcache *bc __unused,
                                struct ext4_buf *buf __unused, int res,
                                void *arg);

/*
 * This routine is only suitable to committed transactions. */
static void jbd_journal_flush_trans(struct jbd_trans *trans) {
    struct jbd_buf *jbd_buf, *tmp;
    struct jbd_journal *journal = trans->journal;
    struct ext4_fs *fs = journal->jbd_fs->inode_ref.fs;
    void *tmp_data = ext4_malloc(journal->block_size);
    ext4_assert(tmp_data);

    TAILQ_FOREACH_SAFE(jbd_buf, &trans->buf_queue, buf_node, tmp) {
        struct ext4_buf *buf;
        struct ext4_block block;
        /* The buffer is not yet flushed. */
        buf =
            ext4_bcache_find_get(fs->bdev->bc, &block, jbd_buf->block_rec->lba);
        if (!(buf && ext4_bcache_test_flag(buf, BC_UPTODATE) &&
              jbd_buf->block_rec->trans == trans)) {
            int r;
            struct ext4_block jbd_block = EXT4_BLOCK_ZERO();
            r = jbd_block_get(journal->jbd_fs, &jbd_block, jbd_buf->jbd_lba);
            ext4_assert(r == EOK);
            memcpy(tmp_data, jbd_block.data, journal->block_size);
            ext4_block_set(fs->bdev, &jbd_block);
            r = ext4_blocks_set_direct(fs->bdev, tmp_data,
                                       jbd_buf->block_rec->lba, 1);
            jbd_trans_end_write(fs->bdev->bc, buf, r, jbd_buf);
        } else
            ext4_block_flush_buf(fs->bdev, buf);

        if (buf)
            ext4_block_set(fs->bdev, &block);
    }

    ext4_free(tmp_data);
}

static void jbd_journal_skip_pure_revoke(struct jbd_journal *journal,
                                         struct jbd_trans *trans) {
    journal->start = trans->start_iblock + trans->alloc_blocks;
    wrap(&journal->jbd_fs->sb, journal->start);
    journal->trans_id = trans->trans_id + 1;
    jbd_journal_free_trans(journal, trans, false);
    jbd_journal_write_sb(journal);
}

void jbd_journal_purge_cp_trans(struct jbd_journal *journal, bool flush,
                                bool once) {
    struct jbd_trans *trans;
    while ((trans = TAILQ_FIRST(&journal->cp_queue))) {
        if (!trans->data_cnt) {
            TAILQ_REMOVE(&journal->cp_queue, trans, trans_node);
            jbd_journal_skip_pure_revoke(journal, trans);
        } else {
            if (trans->data_cnt == trans->written_cnt) {
                journal->start = trans->start_iblock + trans->alloc_blocks;
                wrap(&journal->jbd_fs->sb, journal->start);
                journal->trans_id = trans->trans_id + 1;
                TAILQ_REMOVE(&journal->cp_queue, trans, trans_node);
                jbd_journal_free_trans(journal, trans, false);
                jbd_journal_write_sb(journal);
            } else if (!flush) {
                journal->start = trans->start_iblock;
                wrap(&journal->jbd_fs->sb, journal->start);
                journal->trans_id = trans->trans_id;
                jbd_journal_write_sb(journal);
                break;
            } else
                jbd_journal_flush_trans(trans);
        }
        if (once)
            break;
    }
}

/**@brief  Stop accessing the journal.
 * @param  journal current journal session
 * @return standard error code*/
int jbd_journal_stop(struct jbd_journal *journal) {
    int r;
    struct jbd_fs *jbd_fs = journal->jbd_fs;
    uint32_t features_incompatible;

    /* Make sure that journalled content have reached
     * the disk.*/
    jbd_journal_purge_cp_trans(journal, true, false);

    /* There should be no block record in this journal
     * session. */
    if (!RB_EMPTY(&journal->block_rec_root))
        ext4_dbg(DEBUG_JBD, DBG_WARN "There are still block records "
                                     "in this journal session!\n");

    features_incompatible =
        ext4_get32(&jbd_fs->inode_ref.fs->sb, features_incompatible);
    features_incompatible &= ~EXT4_FINCOM_RECOVER;
    ext4_set32(&jbd_fs->inode_ref.fs->sb, features_incompatible,
               features_incompatible);
    r = ext4_sb_write(jbd_fs->bdev, &jbd_fs->inode_ref.fs->sb);
    if (r != EOK)
        return r;

    journal->start = 0;
    journal->trans_id = 0;
    jbd_journal_write_sb(journal);
    return jbd_write_sb(journal->jbd_fs);
}

/**@brief  Allocate a block in the journal.
 * @param  journal current journal session
 * @param  trans transaction
 * @return allocated block address*/
static uint32_t jbd_journal_alloc_block(struct jbd_journal *journal,
                                        struct jbd_trans *trans) {
    uint32_t start_block;

    start_block = journal->last++;
    trans->alloc_blocks++;
    wrap(&journal->jbd_fs->sb, journal->last);

    /* If there is no space left, flush just one journalled
     * transaction.*/
    if (journal->last == journal->start) {
        jbd_journal_purge_cp_trans(journal, true, true);
        ext4_assert(journal->last != journal->start);
    }

    return start_block;
}

static struct jbd_block_rec *
jbd_trans_block_rec_lookup(struct jbd_journal *journal, ext4_fsblk_t lba) {
    struct jbd_block_rec tmp = {.lba = lba};

    return RB_FIND(jbd_block, &journal->block_rec_root, &tmp);
}

static void jbd_trans_change_ownership(struct jbd_block_rec *block_rec,
                                       struct jbd_trans *new_trans) {
    LIST_REMOVE(block_rec, tbrec_node);
    if (new_trans) {
        /* Now this block record belongs to this transaction. */
        LIST_INSERT_HEAD(&new_trans->tbrec_list, block_rec, tbrec_node);
    }
    block_rec->trans = new_trans;
}

static inline struct jbd_block_rec *
jbd_trans_insert_block_rec(struct jbd_trans *trans, ext4_fsblk_t lba) {
    struct jbd_block_rec *block_rec;
    block_rec = jbd_trans_block_rec_lookup(trans->journal, lba);
    if (block_rec) {
        jbd_trans_change_ownership(block_rec, trans);
        return block_rec;
    }
    block_rec = ext4_calloc(1, sizeof(struct jbd_block_rec));
    if (!block_rec)
        return NULL;

    block_rec->lba = lba;
    block_rec->trans = trans;
    TAILQ_INIT(&block_rec->dirty_buf_queue);
    LIST_INSERT_HEAD(&trans->tbrec_list, block_rec, tbrec_node);
    RB_INSERT(jbd_block, &trans->journal->block_rec_root, block_rec);
    return block_rec;
}

/*
 * This routine will do the dirty works.
 */
static void jbd_trans_finish_callback(struct jbd_journal *journal,
                                      const struct jbd_trans *trans,
                                      struct jbd_block_rec *block_rec,
                                      bool abort, bool revoke) {
    struct ext4_fs *fs = journal->jbd_fs->inode_ref.fs;
    if (block_rec->trans != trans)
        return;

    if (!abort) {
        struct jbd_buf *jbd_buf, *tmp;
        TAILQ_FOREACH_SAFE(jbd_buf, &block_rec->dirty_buf_queue, dirty_buf_node,
                           tmp) {
            jbd_trans_end_write(fs->bdev->bc, NULL, EOK, jbd_buf);
        }
    } else {
        /*
         * We have to roll back data if the block is going to be
         * aborted.
         */
        struct jbd_buf *jbd_buf;
        struct ext4_block jbd_block = EXT4_BLOCK_ZERO(),
                          block = EXT4_BLOCK_ZERO();
        jbd_buf = TAILQ_LAST(&block_rec->dirty_buf_queue, jbd_buf_dirty);
        if (jbd_buf) {
            if (!revoke) {
                int r;
                r = ext4_block_get_noread(fs->bdev, &block, block_rec->lba);
                ext4_assert(r == EOK);
                r = jbd_block_get(journal->jbd_fs, &jbd_block,
                                  jbd_buf->jbd_lba);
                ext4_assert(r == EOK);
                memcpy(block.data, jbd_block.data, journal->block_size);

                jbd_trans_change_ownership(block_rec, jbd_buf->trans);

                block.buf->end_write = jbd_trans_end_write;
                block.buf->end_write_arg = jbd_buf;

                ext4_bcache_set_flag(jbd_block.buf, BC_TMP);
                ext4_bcache_set_dirty(block.buf);

                ext4_block_set(fs->bdev, &jbd_block);
                ext4_block_set(fs->bdev, &block);
                return;
            } else {
                /* The revoked buffer is yet written. */
                jbd_trans_change_ownership(block_rec, jbd_buf->trans);
            }
        }
    }
}

static inline void jbd_trans_remove_block_rec(struct jbd_journal *journal,
                                              struct jbd_block_rec *block_rec,
                                              struct jbd_trans *trans) {
    /* If this block record doesn't belong to this transaction,
     * give up.*/
    if (block_rec->trans == trans) {
        LIST_REMOVE(block_rec, tbrec_node);
        RB_REMOVE(jbd_block, &journal->block_rec_root, block_rec);
        ext4_free(block_rec);
    }
}

/**@brief  Add block to a transaction and mark it dirty.
 * @param  trans transaction
 * @param  block block descriptor
 * @return standard error code*/
int jbd_trans_set_block_dirty(struct jbd_trans *trans,
                              struct ext4_block *block) {
    struct jbd_buf *jbd_buf;
    struct jbd_revoke_rec *rec, tmp_rec = {.lba = block->lb_id};
    struct jbd_block_rec *block_rec;

    if (block->buf->end_write == jbd_trans_end_write) {
        jbd_buf = block->buf->end_write_arg;
        if (jbd_buf && jbd_buf->trans == trans)
            return EOK;
    }
    jbd_buf = ext4_calloc(1, sizeof(struct jbd_buf));
    if (!jbd_buf)
        return ENOMEM;

    if ((block_rec = jbd_trans_insert_block_rec(trans, block->lb_id)) == NULL) {
        ext4_free(jbd_buf);
        return ENOMEM;
    }

    TAILQ_INSERT_TAIL(&block_rec->dirty_buf_queue, jbd_buf, dirty_buf_node);

    jbd_buf->block_rec = block_rec;
    jbd_buf->trans = trans;
    jbd_buf->block = *block;
    ext4_bcache_inc_ref(block->buf);

    /* If the content reach the disk, notify us
     * so that we may do a checkpoint. */
    block->buf->end_write = jbd_trans_end_write;
    block->buf->end_write_arg = jbd_buf;

    trans->data_cnt++;
    TAILQ_INSERT_HEAD(&trans->buf_queue, jbd_buf, buf_node);

    ext4_bcache_set_dirty(block->buf);
    rec = RB_FIND(jbd_revoke_tree, &trans->revoke_root, &tmp_rec);
    if (rec) {
        RB_REMOVE(jbd_revoke_tree, &trans->revoke_root, rec);
        ext4_free(rec);
    }

    return EOK;
}

/**@brief  Add block to be revoked to a transaction
 * @param  trans transaction
 * @param  lba logical block address
 * @return standard error code*/
int jbd_trans_revoke_block(struct jbd_trans *trans, ext4_fsblk_t lba) {
    struct jbd_revoke_rec tmp_rec = {.lba = lba}, *rec;
    rec = RB_FIND(jbd_revoke_tree, &trans->revoke_root, &tmp_rec);
    if (rec)
        return EOK;

    rec = ext4_calloc(1, sizeof(struct jbd_revoke_rec));
    if (!rec)
        return ENOMEM;

    rec->lba = lba;
    RB_INSERT(jbd_revoke_tree, &trans->revoke_root, rec);
    return EOK;
}

/**@brief  Try to add block to be revoked to a transaction.
 *         If @lba still remains in an transaction on checkpoint
 *         queue, add @lba as a revoked block to the transaction.
 * @param  trans transaction
 * @param  lba logical block address
 * @return standard error code*/
int jbd_trans_try_revoke_block(struct jbd_trans *trans, ext4_fsblk_t lba) {
    struct jbd_journal *journal = trans->journal;
    struct jbd_block_rec *block_rec = jbd_trans_block_rec_lookup(journal, lba);

    if (block_rec) {
        if (block_rec->trans == trans) {
            struct jbd_buf *jbd_buf =
                TAILQ_LAST(&block_rec->dirty_buf_queue, jbd_buf_dirty);
            /* If there are still unwritten buffers. */
            if (TAILQ_FIRST(&block_rec->dirty_buf_queue) != jbd_buf)
                jbd_trans_revoke_block(trans, lba);
        } else
            jbd_trans_revoke_block(trans, lba);
    }

    return EOK;
}

/**@brief  Free a transaction
 * @param  journal current journal session
 * @param  trans transaction
 * @param  abort discard all the modifications on the block?*/
void jbd_journal_free_trans(struct jbd_journal *journal,
                            struct jbd_trans *trans, bool abort) {
    struct jbd_buf *jbd_buf, *tmp;
    struct jbd_revoke_rec *rec, *tmp2;
    struct jbd_block_rec *block_rec, *tmp3;
    struct ext4_fs *fs = journal->jbd_fs->inode_ref.fs;
    TAILQ_FOREACH_SAFE(jbd_buf, &trans->buf_queue, buf_node, tmp) {
        block_rec = jbd_buf->block_rec;
        if (abort) {
            jbd_buf->block.buf->end_write = NULL;
            jbd_buf->block.buf->end_write_arg = NULL;
            ext4_bcache_clear_dirty(jbd_buf->block.buf);
            ext4_block_set(fs->bdev, &jbd_buf->block);
        }

        TAILQ_REMOVE(&jbd_buf->block_rec->dirty_buf_queue, jbd_buf,
                     dirty_buf_node);
        jbd_trans_finish_callback(journal, trans, block_rec, abort, false);
        TAILQ_REMOVE(&trans->buf_queue, jbd_buf, buf_node);
        ext4_free(jbd_buf);
    }
    RB_FOREACH_SAFE(rec, jbd_revoke_tree, &trans->revoke_root, tmp2) {
        RB_REMOVE(jbd_revoke_tree, &trans->revoke_root, rec);
        ext4_free(rec);
    }
    LIST_FOREACH_SAFE(block_rec, &trans->tbrec_list, tbrec_node, tmp3) {
        jbd_trans_remove_block_rec(journal, block_rec, trans);
    }

    ext4_free(trans);
}

/**@brief  Write commit block for a transaction
 * @param  trans transaction
 * @return standard error code*/
static int jbd_trans_write_commit_block(struct jbd_trans *trans) {
    int rc;
    struct ext4_block block;
    struct jbd_commit_header *header;
    uint32_t commit_iblock;
    struct jbd_journal *journal = trans->journal;

    commit_iblock = jbd_journal_alloc_block(journal, trans);

    rc = jbd_block_get_noread(journal->jbd_fs, &block, commit_iblock);
    if (rc != EOK)
        return rc;

    header = (struct jbd_commit_header *)block.data;
    jbd_set32(&header->header, magic, JBD_MAGIC_NUMBER);
    jbd_set32(&header->header, blocktype, JBD_COMMIT_BLOCK);
    jbd_set32(&header->header, sequence, trans->trans_id);

    if (JBD_HAS_INCOMPAT_FEATURE(&journal->jbd_fs->sb,
                                 JBD_FEATURE_COMPAT_CHECKSUM)) {
        header->chksum_type = JBD_CRC32_CHKSUM;
        header->chksum_size = JBD_CRC32_CHKSUM_SIZE;
        jbd_set32(header, chksum[0], trans->data_csum);
    }
    jbd_commit_csum_set(journal->jbd_fs, header);
    ext4_bcache_set_dirty(block.buf);
    ext4_bcache_set_flag(block.buf, BC_TMP);
    rc = jbd_block_set(journal->jbd_fs, &block);
    return rc;
}

/**@brief  Write descriptor block for a transaction
 * @param  journal current journal session
 * @param  trans transaction
 * @return standard error code*/
static int jbd_journal_prepare(struct jbd_journal *journal,
                               struct jbd_trans *trans) {
    int rc = EOK, i = 0;
    struct ext4_block desc_block = EXT4_BLOCK_ZERO(),
                      data_block = EXT4_BLOCK_ZERO();
    int32_t tag_tbl_size = 0;
    uint32_t desc_iblock = 0;
    uint32_t data_iblock = 0;
    char *tag_start = NULL, *tag_ptr = NULL;
    struct jbd_buf *jbd_buf, *tmp;
    struct ext4_fs *fs = journal->jbd_fs->inode_ref.fs;
    uint32_t checksum = EXT4_CRC32_INIT;
    struct jbd_bhdr *bhdr = NULL;
    void *data;

    /* Try to remove any non-dirty buffers from the tail of
     * buf_queue. */
    TAILQ_FOREACH_REVERSE_SAFE(jbd_buf, &trans->buf_queue, jbd_trans_buf,
                               buf_node, tmp) {
        struct jbd_revoke_rec tmp_rec = {.lba = jbd_buf->block_rec->lba};
        /* We stop the iteration when we find a dirty buffer. */
        if (ext4_bcache_test_flag(jbd_buf->block.buf, BC_DIRTY))
            break;

        TAILQ_REMOVE(&jbd_buf->block_rec->dirty_buf_queue, jbd_buf,
                     dirty_buf_node);

        jbd_buf->block.buf->end_write = NULL;
        jbd_buf->block.buf->end_write_arg = NULL;
        jbd_trans_finish_callback(
            journal, trans, jbd_buf->block_rec, true,
            RB_FIND(jbd_revoke_tree, &trans->revoke_root, &tmp_rec));
        jbd_trans_remove_block_rec(journal, jbd_buf->block_rec, trans);
        trans->data_cnt--;

        ext4_block_set(fs->bdev, &jbd_buf->block);
        TAILQ_REMOVE(&trans->buf_queue, jbd_buf, buf_node);
        ext4_free(jbd_buf);
    }

    TAILQ_FOREACH_SAFE(jbd_buf, &trans->buf_queue, buf_node, tmp) {
        struct tag_info tag_info;
        bool uuid_exist = false;
        bool is_escape = false;
        struct jbd_revoke_rec tmp_rec = {.lba = jbd_buf->block_rec->lba};
        if (!ext4_bcache_test_flag(jbd_buf->block.buf, BC_DIRTY)) {
            TAILQ_REMOVE(&jbd_buf->block_rec->dirty_buf_queue, jbd_buf,
                         dirty_buf_node);

            jbd_buf->block.buf->end_write = NULL;
            jbd_buf->block.buf->end_write_arg = NULL;

            /* The buffer has not been modified, just release
             * that jbd_buf. */
            jbd_trans_finish_callback(
                journal, trans, jbd_buf->block_rec, true,
                RB_FIND(jbd_revoke_tree, &trans->revoke_root, &tmp_rec));
            jbd_trans_remove_block_rec(journal, jbd_buf->block_rec, trans);
            trans->data_cnt--;

            ext4_block_set(fs->bdev, &jbd_buf->block);
            TAILQ_REMOVE(&trans->buf_queue, jbd_buf, buf_node);
            ext4_free(jbd_buf);
            continue;
        }
        checksum = jbd_block_csum(journal->jbd_fs, jbd_buf->block.data,
                                  checksum, trans->trans_id);
        if (((struct jbd_bhdr *)jbd_buf->block.data)->magic ==
            to_be32(JBD_MAGIC_NUMBER))
            is_escape = true;

    again:
        if (!desc_iblock) {
            desc_iblock = jbd_journal_alloc_block(journal, trans);
            rc =
                jbd_block_get_noread(journal->jbd_fs, &desc_block, desc_iblock);
            if (rc != EOK)
                break;

            bhdr = (struct jbd_bhdr *)desc_block.data;
            jbd_set32(bhdr, magic, JBD_MAGIC_NUMBER);
            jbd_set32(bhdr, blocktype, JBD_DESCRIPTOR_BLOCK);
            jbd_set32(bhdr, sequence, trans->trans_id);

            tag_start = (char *)(bhdr + 1);
            tag_ptr = tag_start;
            uuid_exist = true;
            tag_tbl_size = journal->block_size - sizeof(struct jbd_bhdr);

            if (jbd_has_csum(&journal->jbd_fs->sb))
                tag_tbl_size -= sizeof(struct jbd_block_tail);

            if (!trans->start_iblock)
                trans->start_iblock = desc_iblock;

            ext4_bcache_set_dirty(desc_block.buf);
            ext4_bcache_set_flag(desc_block.buf, BC_TMP);
        }
        tag_info.block = jbd_buf->block.lb_id;
        tag_info.uuid_exist = uuid_exist;
        tag_info.is_escape = is_escape;
        if (i == trans->data_cnt - 1)
            tag_info.last_tag = true;
        else
            tag_info.last_tag = false;

        tag_info.checksum = checksum;

        if (uuid_exist)
            memcpy(tag_info.uuid, journal->jbd_fs->sb.uuid, UUID_SIZE);

        rc = jbd_write_block_tag(journal->jbd_fs, tag_ptr, tag_tbl_size,
                                 &tag_info);
        if (rc != EOK) {
            jbd_meta_csum_set(journal->jbd_fs, bhdr);
            desc_iblock = 0;
            rc = jbd_block_set(journal->jbd_fs, &desc_block);
            if (rc != EOK)
                break;

            goto again;
        }

        data_iblock = jbd_journal_alloc_block(journal, trans);
        rc = jbd_block_get_noread(journal->jbd_fs, &data_block, data_iblock);
        if (rc != EOK) {
            desc_iblock = 0;
            ext4_bcache_clear_dirty(desc_block.buf);
            jbd_block_set(journal->jbd_fs, &desc_block);
            break;
        }

        data = data_block.data;
        memcpy(data, jbd_buf->block.data, journal->block_size);
        if (is_escape)
            ((struct jbd_bhdr *)data)->magic = 0;

        ext4_bcache_set_dirty(data_block.buf);
        ext4_bcache_set_flag(data_block.buf, BC_TMP);
        rc = jbd_block_set(journal->jbd_fs, &data_block);
        if (rc != EOK) {
            desc_iblock = 0;
            ext4_bcache_clear_dirty(desc_block.buf);
            jbd_block_set(journal->jbd_fs, &desc_block);
            break;
        }
        jbd_buf->jbd_lba = data_iblock;

        tag_ptr += tag_info.tag_bytes;
        tag_tbl_size -= tag_info.tag_bytes;

        i++;
    }
    if (rc == EOK && desc_iblock) {
        jbd_meta_csum_set(journal->jbd_fs, (struct jbd_bhdr *)bhdr);
        trans->data_csum = checksum;
        rc = jbd_block_set(journal->jbd_fs, &desc_block);
    }

    return rc;
}

/**@brief  Write revoke block for a transaction
 * @param  journal current journal session
 * @param  trans transaction
 * @return standard error code*/
static int jbd_journal_prepare_revoke(struct jbd_journal *journal,
                                      struct jbd_trans *trans) {
    int rc = EOK, i = 0;
    struct ext4_block desc_block = EXT4_BLOCK_ZERO();
    int32_t tag_tbl_size = 0;
    uint32_t desc_iblock = 0;
    char *blocks_entry = NULL;
    struct jbd_revoke_rec *rec, *tmp;
    struct jbd_revoke_header *header = NULL;
    int32_t record_len = 4;
    struct jbd_bhdr *bhdr = NULL;

    if (JBD_HAS_INCOMPAT_FEATURE(&journal->jbd_fs->sb,
                                 JBD_FEATURE_INCOMPAT_64BIT))
        record_len = 8;

    RB_FOREACH_SAFE(rec, jbd_revoke_tree, &trans->revoke_root, tmp) {
    again:
        if (!desc_iblock) {
            desc_iblock = jbd_journal_alloc_block(journal, trans);
            rc =
                jbd_block_get_noread(journal->jbd_fs, &desc_block, desc_iblock);
            if (rc != EOK)
                break;

            bhdr = (struct jbd_bhdr *)desc_block.data;
            jbd_set32(bhdr, magic, JBD_MAGIC_NUMBER);
            jbd_set32(bhdr, blocktype, JBD_REVOKE_BLOCK);
            jbd_set32(bhdr, sequence, trans->trans_id);

            header = (struct jbd_revoke_header *)bhdr;
            blocks_entry = (char *)(header + 1);
            tag_tbl_size =
                journal->block_size - sizeof(struct jbd_revoke_header);

            if (jbd_has_csum(&journal->jbd_fs->sb))
                tag_tbl_size -= sizeof(struct jbd_block_tail);

            if (!trans->start_iblock)
                trans->start_iblock = desc_iblock;

            ext4_bcache_set_dirty(desc_block.buf);
            ext4_bcache_set_flag(desc_block.buf, BC_TMP);
        }

        if (tag_tbl_size < record_len) {
            jbd_set32(header, count, journal->block_size - tag_tbl_size);
            jbd_meta_csum_set(journal->jbd_fs, bhdr);
            bhdr = NULL;
            desc_iblock = 0;
            header = NULL;
            rc = jbd_block_set(journal->jbd_fs, &desc_block);
            if (rc != EOK)
                break;

            goto again;
        }
        if (record_len == 8) {
            uint64_t *blocks = (uint64_t *)blocks_entry;
            *blocks = to_be64(rec->lba);
        } else {
            uint32_t *blocks = (uint32_t *)blocks_entry;
            *blocks = to_be32((uint32_t)rec->lba);
        }
        blocks_entry += record_len;
        tag_tbl_size -= record_len;

        i++;
    }
    if (rc == EOK && desc_iblock) {
        if (header != NULL)
            jbd_set32(header, count, journal->block_size - tag_tbl_size);

        jbd_meta_csum_set(journal->jbd_fs, bhdr);
        rc = jbd_block_set(journal->jbd_fs, &desc_block);
    }

    return rc;
}

/**@brief  Put references of block descriptors in a transaction.
 * @param  journal current journal session
 * @param  trans transaction*/
void jbd_journal_cp_trans(struct jbd_journal *journal,
                          struct jbd_trans *trans) {
    struct jbd_buf *jbd_buf, *tmp;
    struct ext4_fs *fs = journal->jbd_fs->inode_ref.fs;
    TAILQ_FOREACH_SAFE(jbd_buf, &trans->buf_queue, buf_node, tmp) {
        struct ext4_block block = jbd_buf->block;
        ext4_block_set(fs->bdev, &block);
    }
}

/**@brief  Update the start block of the journal when
 *         all the contents in a transaction reach the disk.*/
static void jbd_trans_end_write(struct ext4_bcache *bc __unused,
                                struct ext4_buf *buf, int res, void *arg) {
    struct jbd_buf *jbd_buf = arg;
    struct jbd_trans *trans = jbd_buf->trans;
    struct jbd_block_rec *block_rec = jbd_buf->block_rec;
    struct jbd_journal *journal = trans->journal;
    bool first_in_queue = trans == TAILQ_FIRST(&journal->cp_queue);
    if (res != EOK)
        trans->error = res;

    TAILQ_REMOVE(&trans->buf_queue, jbd_buf, buf_node);
    TAILQ_REMOVE(&block_rec->dirty_buf_queue, jbd_buf, dirty_buf_node);

    jbd_trans_finish_callback(journal, trans, jbd_buf->block_rec, false, false);
    if (block_rec->trans == trans && buf) {
        /* Clear the end_write and end_write_arg fields. */
        buf->end_write = NULL;
        buf->end_write_arg = NULL;
    }

    ext4_free(jbd_buf);

    trans->written_cnt++;
    if (trans->written_cnt == trans->data_cnt) {
        /* If it is the first transaction on checkpoint queue,
         * we will shift the start of the journal to the next
         * transaction, and remove subsequent written
         * transactions from checkpoint queue until we find
         * an unwritten one. */
        if (first_in_queue) {
            journal->start = trans->start_iblock + trans->alloc_blocks;
            wrap(&journal->jbd_fs->sb, journal->start);
            journal->trans_id = trans->trans_id + 1;
            TAILQ_REMOVE(&journal->cp_queue, trans, trans_node);
            jbd_journal_free_trans(journal, trans, false);

            jbd_journal_purge_cp_trans(journal, false, false);
            jbd_journal_write_sb(journal);
            jbd_write_sb(journal->jbd_fs);
        }
    }
}

/**@brief  Commit a transaction to the journal immediately.
 * @param  journal current journal session
 * @param  trans transaction
 * @return standard error code*/
static int __jbd_journal_commit_trans(struct jbd_journal *journal,
                                      struct jbd_trans *trans) {
    int rc = EOK;
    uint32_t last = journal->last;
    struct jbd_revoke_rec *rec, *tmp;

    trans->trans_id = journal->alloc_trans_id;
    rc = jbd_journal_prepare(journal, trans);
    if (rc != EOK)
        goto Finish;

    rc = jbd_journal_prepare_revoke(journal, trans);
    if (rc != EOK)
        goto Finish;

    if (TAILQ_EMPTY(&trans->buf_queue) && RB_EMPTY(&trans->revoke_root)) {
        /* Since there are no entries in both buffer list
         * and revoke entry list, we do not consider trans as
         * complete transaction and just return EOK.*/
        jbd_journal_free_trans(journal, trans, false);
        goto Finish;
    }

    rc = jbd_trans_write_commit_block(trans);
    if (rc != EOK)
        goto Finish;

    journal->alloc_trans_id++;

    /* Complete the checkpoint of buffers which are revoked. */
    RB_FOREACH_SAFE(rec, jbd_revoke_tree, &trans->revoke_root, tmp) {
        struct jbd_block_rec *block_rec =
            jbd_trans_block_rec_lookup(journal, rec->lba);
        struct jbd_buf *jbd_buf = NULL;
        if (block_rec)
            jbd_buf = TAILQ_LAST(&block_rec->dirty_buf_queue, jbd_buf_dirty);
        if (jbd_buf) {
            struct ext4_buf *buf;
            struct ext4_block block = EXT4_BLOCK_ZERO();
            /*
             * We do this to reset the ext4_buf::end_write and
             * ext4_buf::end_write_arg fields so that the checkpoint
             * callback won't be triggered again.
             */
            buf = ext4_bcache_find_get(journal->jbd_fs->bdev->bc, &block,
                                       jbd_buf->block_rec->lba);
            jbd_trans_end_write(journal->jbd_fs->bdev->bc, buf, EOK, jbd_buf);
            if (buf)
                ext4_block_set(journal->jbd_fs->bdev, &block);
        }
    }

    if (TAILQ_EMPTY(&journal->cp_queue)) {
        /*
         * This transaction is going to be the first object in the
         * checkpoint queue.
         * When the first transaction in checkpoint queue is completely
         * written to disk, we shift the tail of the log to right.
         */
        if (trans->data_cnt) {
            journal->start = trans->start_iblock;
            wrap(&journal->jbd_fs->sb, journal->start);
            journal->trans_id = trans->trans_id;
            jbd_journal_write_sb(journal);
            jbd_write_sb(journal->jbd_fs);
            TAILQ_INSERT_TAIL(&journal->cp_queue, trans, trans_node);
            jbd_journal_cp_trans(journal, trans);
        } else {
            journal->start = trans->start_iblock + trans->alloc_blocks;
            wrap(&journal->jbd_fs->sb, journal->start);
            journal->trans_id = trans->trans_id + 1;
            jbd_journal_write_sb(journal);
            jbd_journal_free_trans(journal, trans, false);
        }
    } else {
        /* No need to do anything to the JBD superblock. */
        TAILQ_INSERT_TAIL(&journal->cp_queue, trans, trans_node);
        if (trans->data_cnt)
            jbd_journal_cp_trans(journal, trans);
    }
Finish:
    if (rc != EOK && rc != ENOSPC) {
        journal->last = last;
        jbd_journal_free_trans(journal, trans, true);
    }
    return rc;
}

/**@brief  Allocate a new transaction
 * @param  journal current journal session
 * @return transaction allocated*/
struct jbd_trans *jbd_journal_new_trans(struct jbd_journal *journal) {
    struct jbd_trans *trans = NULL;
    trans = ext4_calloc(1, sizeof(struct jbd_trans));
    if (!trans)
        return NULL;

    /* We will assign a trans_id to this transaction,
     * once it has been committed.*/
    trans->journal = journal;
    trans->data_csum = EXT4_CRC32_INIT;
    trans->error = EOK;
    TAILQ_INIT(&trans->buf_queue);
    return trans;
}

/**@brief  Commit a transaction to the journal immediately.
 * @param  journal current journal session
 * @param  trans transaction
 * @return standard error code*/
int jbd_journal_commit_trans(struct jbd_journal *journal,
                             struct jbd_trans *trans) {
    int r = EOK;
    r = __jbd_journal_commit_trans(journal, trans);
    return r;
}

/**
 * @}
 */
